Optical shutter system and methods related thereto

ABSTRACT

An optical shutter system and methods of establishing the relative positions of the elements of the system are disclosed for use in simulated animated displays, in enabling viewing an image where the viewer and image are moving relative to one another at a rapid rate, and in related applications. A series of images which may be progressively varied and carried on transparencies are associated with the optical shutter system. The shutter system includes a linear light source and a pellucid sheet and may include one or more reflective surfaces selectively oriented with respect to the transparencies on the side of the transparency opposite the viewer. When there is effective relative movement between the viewer and the transparencies, the light appears to sweep across each transparency, progressively illuminating linear adjacent segments of each image; thus the viewer perceives a motion picture composed of the progressively illuminated image segments. Methods are also disclosed for establishing the orientation of the elements of the optical shutter system relative to each other and to the transparency to be observed. The methods take into account the range of expected viewing distances and the dimensions of the transparency, as well as the space available in varying environments for mounting the system, the light intensity desired and the repetition rate required for optimum viewing.

[73] Assignee:

ited States Mitchell atent [54] OPTICAL SHUTTER SYSTEM AND METHODSRELATED THERETO [52] U.S. Cl ..352/l00, 352/81 [51] Int. Cl. ..G03b17/02 [58] Field ofSearch ..352/100,81;40/l25 M, 137

[56] References Cited UNITED STATES PATENTS 742,632 10/1903 Hadden..352/l00 Primary Examiner-Donald O. Woodiel Attorney-Pendleton, Neuman,Williams & Anderson [57] ABSTRACT An optical shutter system and methodsof establishing the [4 1 Apr. 4, i972 relative positions of the elementsof the system are disclosed for use in simulated animated displays, inenabling viewing an image where the viewer and image are moving relativeto one another at a rapid rate, and in related applications. A series ofimages which may be progressively varied and carried on transparenciesare associated with the optical shutter system. The shutter systemincludes a linear light source and a pellucid sheet and may include oneor more reflective surfaces selectively oriented with respect to thetransparencies on the side of the transparency opposite the viewer. Whenthere is effective relative movement between the viewer and thetransparencies, the light appears to sweep across each transparency,progressively illuminating linear adjacent segments of each image; thusthe viewer perceives a motion picture composed of the progressivelyilluminated image segments.

Methods are also disclosed for establishing the orientation of theelements of the optical shutter system relative to each other and to thetransparency'to be observed. The methods take into account the range ofexpected viewing distances and the dimensions of the transparency, aswell as the space availa ble in varying environments for mounting thesystem, the light intensity desired and the repetition rate required foroptimum viewing.

25 Claims, 12 Drawing Figures PATENTEDAFR 4 I972 SHEET 1 [IF 4PATENTEDAPR 4:972 3,653.753

SHEET 3 [IF 4 PATENTEDAPR 41912 3,653,753

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OPTICAL SHUTTER SYSTEM AND METHODS RELATED THERETO BACKGROUND OF THEINVENTION The present invention relates to an optical shutter and moreparticularly to a display system, incorporating the shutter, whichpresents a simulated display to a viewer where there is relative motionbetween the viewer and the light source.

An exemplary field of use for this invention is an installationincluding a plurality of the shutters comprising linear light sourcesassociated with pellucid sheets bearing the images from an animateddisplay to be presented on the wall of a subway tunnel, elevator shaftor similar area. The movement of the subway train provides relativemotion between the light sources, animated scenes and the observer, andit is this relative movement between an observer, a pellucid image, anda linear light source that comprises the operating mechanism of theshutter. Among the problems presented by such an installation are thatthe permissible depth of the installation is limited by the availablespace between the mounting wall and the side of the train. Theinstallation must also be designed for inexpensive maintenance andreplacement of the animated scenes and the other elements of theinstallation. Moreover, the installation must be arranged so that theanimated display is clearly presented to the viewer, and not blurred bythe speed of passage of the train.

Many attempts have been made to produce a simulated animated displaywhere there is relative motion between a viewer and a fixture carrying asuccession of animated images. Some such systems have used the relativemotion as a control means for a switching system or the like. Typicalprior art systems are disclosed in U.S. Pat. Nos. 3,463,581; 2,833,176;3,329,475; 3,480,352; 2,438,878; 2,401,271; 2,299,731; 3,261,120; and2,618,067. Some of these patents utilize scanning assemblies includingconvergent, anamorphic or other special purpose lenses located betweenthe animated scenes and the observer. Such lenses increase the cost ofthe installation, and require considerable maintenance. Moreover, noneof these specialpurpose lens systems incorporate a lighting arrangementto .render them usable in areas of limited ambient light or utilize theunique principle of this invention.

Other patents disclose a display system including a series of picturesdirectly illuminated by individually triggered light sources, lightswitches, mechanical shutters and the like, The system is mounted on awall beside the moving vehicle whose passage triggers the momentaryilluminating flash when the vehicle is adjacent each picture. Suchsystems result in blurring for many reasons, one being that noeconomically feasible light source provides the short duration, highintensity light required and timing becomes critical. Such systems wouldbe very expensive.

SUMMARY OF THE INVENTION Therefore, an object of the present inventionis to present a reconstructed display to a viewer in motion relative tothe display.

Another object of the invention is to provide a display system usable inareas of limited or unlimited ambient light.

Another object of the invention is to provide an optical shutter adaptedfor use in an animated display system.

Another object of the invention is to provide an animated display systemincluding an optical shutter whose basic elements may be modified inaccordance with the methods disclosed to meet the limitations imposed byvarying environments.

In the display system in which the optical shutter is disclosed, theshutter system includes a linear light source mounted on one side of apellucid sheet with means being provided for producing relative movementbetween the pellucid sheet and linear source on the one hand and aviewer on the side of the sheet opposite the source. Particularadvantages are gained by using reflective surfaces to relocate the lightto the edge of the sheet. As used herein, the term transparency refersto a particular pellucid sheet and is generally a photographic film forcarrying one image of a series of scenes to be presented to a viewer inmotion relative to the transparency. The reflective surfaces are sodesigned and oriented that as the observer and transparency moverelatively, the vertical line of light appears through the transparencyand traverses the width of the image, presenting the image in successivesegments as the relative positions of observer, image and light change.When a series of units carrying a succession of animated images areobserved, a simulated animated display is perceived by the observer.

DESCRIPTION OF THE DRAWINGS FIG. 11 is a perspective diagrammatic viewof an optical shutter system in accordance with the present invention.

FIG. 2 is a diagrammatic top plan view of portions of another opticalshutter system designed in accordance with the present inventionutilizing reflective surfaces to reduce the depth of the system.

FIG. 3 is an enlarged diagrammatic top plan view of the optical shutterof the system of FIG. 2.

FIG. is an exploded diagrammatic right side view of the optical shutterof FIG. 3 illustrating the minimum relative height of the variouscomponents of the optical shutter of FIG. 3. passenger FIG. 5 is adiagrammatic top plan view of an optical shutter illustrating the widthof the picture in relation to the ratio of viewing distance to effectivelight spacing.

FIG. 6 is a diagrammatic top plan view of a portion of anotherembodiment of the optical shutter system.

FIG. 7 is a diagrammatic top plan view of a portion of still anotherembodiment of the optical shutter system.

FIG. 8 is a diagrammatic top plan view of a portion of an additionalembodiment of the optical shutter system.

FIG. 9 is a diagrammatic top plan view illustrating an empirical methodof establishing the curvature of the shutter of FIG.

FIG. 10 is a perspective view of a portion of another systemincorporating the optical shutter of FIG. 8 and designed in accordancewith the method of FIG. 9.

FIG. 111 is an elevational view diagrammatically illustrating theapplication of the invention to a subway train and tunnel.

FIG. 12 is a plan view diagrammatically illustrating the application ofFIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawingsand in particular, to FIG. 1, an animated display system 1 isdiagrammatically shown which illustrates the optical and dynamicprinciples incorporated in the present invention. Pellucid sheets 2,which may be photographic transparencies, are mounted in side-by-sidegenerally parallel relationship spaced from a support for an observerrepresented by eye 4. The vertical light source 6 is disposed on theopposite side of the sheets 2 and seen by the observer 4 through thesheets 2. The light source 6 is either very narrow or is masked orbaffled to project a narrow line of light which appears to the observer4 as a horizontally limited segment 7 of the intermediate pellucid sheet2. The observer 4 and sheet or transparency 2 are in relative motion andhis field of vision of the linear light 6 through sheet 2 isapproximately defined by dotted lines 8 and 10. The images carried bythe transparencies 2 may be the same as shown in FIG. 1, orprogressively and gradually varied. They may also comprise groups ofidentical images to create a sequence of stills.

If the observer 4 is moving past a transparency 2a of the display system1 as illustrated by arrows 5, the light from source 6a appears to wipeacross the transparency presenting successive vertical segments 7 of theimage to the observer. For a viewer moving from right to left asindicated by arrow 5, the picture, as perceived, reverses itself so thatthe part of it which is observed first, (the right side), appears to theobserver to be on the left. As the light source 612 is seen through theright side of the next succeeding transparency 2b, the preceding lightsource 6a is also seen through the last or left part of the previousimage 2a, the first or right part being replaced by correspondingsegments of the image on the succeeding transparency. Thus, if eachimage differs slightly from the preceding one, the composite mentalimage formed from the perceived vertical segments appears to be inmotion, thus creating the desired animated display. In order for thissystem to function effectively, the transparencies 2 or other pellucidsheets must minimize the diffusion or refraction of light. In general,the higher the transmissibility of the sheet 2, the more efficient isthe shutter action.

In an embodiment such as that of FIG. 1, the preferred distance from thelight source 6 to the transparency 2 is equal to the expected viewingdistance EVD as shown in FIG. 5. In this case, the width of the imageperceived by the observer is equal to the actual width of thetransparency and the image will be perceived while the observer ismoving a distance equal to twice the width of the transparency 2 along aline parallel to the transparency. If the actual viewing distance isshorter than the distance to the light source 6, the perceived image isnarrower than the width of the transparency; if the viewing distance islonger, the perceived image is wider than the transparency. Therelationship between the viewing distance and the width of the perceivedimage is linear; e.g., at a viewing distance one-half of the expectedviewing distance EVD, the width of the perceived image is one-half ofthe transparency width. Also, the relative travel of the observer andthe sheet 2 and light source 6 are also proportional to the ratio ofdistances from the viewer to the sheet 2 and from the light source 6 tothe sheet 2. Thus, if a 1:1 ratio of distance is employed and the sheets2 abut, the observer would be seeing the segmental reconstruction of twosheets 2 at all times. Conversely, if the sheets 2 are spaced apart bythe width of a sheet and the distance ration is 1:1, the viewer will seeonly one segmental image sequence at a given time.

For an expected viewing distance of several feet, as encountered in asubway tunnel or similar environment, placement of the light source 6behind the transparency at a distance equal to the expected viewingdistance is impractical. In the optical shutter system of thisinvention, the linear light source may be advantageously placed at theside of the transparency and close to the plane thereof and reflectivesurfaces oriented with respect to the transparency and the light sourceso that the virtual image of the light source appears behind thetransparency at the position described in FIG. 1. The exemplaryembodiment of FIG. 6 incorporates a single planar reflective surface. Todetermine the orientation of the reflective surface 20, the actualposition A of the source of the linear light source and the desiredposition B of its virtual image are first established. A triangle isthen formed by drawing rays from the edges C, D of the transparency tothe virtual image position and a central axis from B to I. These raysshould form an isosceles triangle BCD, the virtual image being centeredbehind the transparency. If the light source is not centered or if theangle CBD is too great, the visual impression will be one of an apparentacceleration of the sweeping line segment 7 at the normal position Iwith gradually diminished sweep rates as the angle increases.

Moreover, as the total image is the total visual effect of thesesegments integrated over a short period of time, a large angle or offsetlight source will produce image distortion, effectively stretching theimage for the larger angles. This can, where necessary, be compensatedby introducing distortion into the image on the pellucid sheet 2.

The triangle BCD is effectively folded about a line EF with a reflectivesurface so that the vertex B of the triangle coincides with the actualposition A of the light source 6. A planar reflective surface 20, placedon this fold line or crease EF in accordance with known reflectivetheory, reflects the rays of the linear light emanating from the lightsource 6 to the transparency 2 in the same pattern as if the lightsource were actually located at the virtual image position B. Thus, aviewer moving past the transparency sees a line of light moving with himacross the transparency, illuminating successive sections of thetransparency 2 in the same manner as already described.

The use of a single reflective surface allows for placement of the lightsource close to the edge of the transparency, providing a concomitantreduction in the depth of the installation of up to 50 percent. Furtherreduction is achieved by employing a multiplicity of reflective surfacesto fold the triangle defined by the edges of the transparency and thevirtual image position of the light source. For example, if this schemeis used to display an animated picture on the wall of the subway, aminimum amount of depth is available. An embodiment adapted to thisenvironment is shown in FIG. 3, wherein the triangular segment is foldedtwice by reflective surfaces 30 and 32. To determine their placement,first the position of the rearward edge of the first reflective surfaceis placed at the intersection G of the ray DB with a line 33 definingthe maximum depth of the shutter system. The other criteria establishedfor folding the triangle BCD are secondly, the light source and therearward edge of the second reflective surface should be approximatelylaterally equidistant from the edges of the transparency; and thirdly,the forward edge of the linear light from the light source 6 should passclose behind and preferably parallel to the transparency, with thevertex of the triangle resting on the A, the actual position of thelight source 6. The angular displacement of the reflective surfaces isdetermined by anchoring triangle BCD at the rearward point G on thefirst surface, and adjusting the pitch of the first foldline GH and thepitch and placement of the second foldline JK until the criteriaestablished in the second and third steps are met, bearing in mind thefundamentals of reflective theory. The two reflective surfaces 30 and 32are then placed on the creases GH and JK in the triangle. If triangleBCD is properly folded, the length of a ray from a point on thetransparency is the same whether drawn to the real position A or thevirtual position B of the light source. The light source 6 is locatedfarther laterally from the edge ofthe transparency than in theembodiment of FIG. 6 to optimize the space available. A baffle 34 ispreferably added to the edge of the frame holding the transparency 2 sothat no light from the source 6 can produce false sweeps or ghosts inthe projected image. Baffles should be located in the system whereverthere is a possibility that spurious light can impinge upon the sheet Inan embodiment such as that of FIG. 2 wherein the optical shutter systemprojects a succession of images to a passing observer, a singlefluorescent tube may serve as the light source 40 for two adjacentsheets 2, the tube having baffles to provide two diversely directedlight sources 42 and 44. Because of the lateral relative displacement ofthe light source and the second reflective surface, a dark spaceintervenes between two adjacent transparencies 2a and 2b. However, asalready explained, this is not detrimental because of the visual overlapof the adjacent images as seen by an observer if the images arecontiguous.

If more depth is available and closer lateral spacing is desirable, anoptical shutter using three reflective surfaces 50, 52, 54 as shown inFIG. 7, may be used. The light source is much closer to the transparencyso that the light is less susceptible to observation by the viewer andthe necessity of a baffle is eliminated. A baffle may still be employedwith some beneficial results.

While the system functions in ambient light with very little shieldingit is important that the observer does not see any spurious lightsources through the pellucid sheet. Thus it is preferred that the entireassembly be mounted within a box such as shown in FIGS. 11 and 12 or ina similar housing. Even where space is available and the system isconstructed as in FIG. I, it is preferred that the arrangement beshielded to avoid the impingement of sun light, head lights or otherspurious sources. In some applications the reflectors and a light valvedefining a linear slit can be employed with the slit filled with adiffusive material to constitute a source and sun light can be used asthe source of energy, for example, eliminating the electricallyenergized light source contemplated in FIG. I.

FIG. 4 is a diagram taken perpendicular to the direction of relativemovement. It illustrates that the relative heights of the elements ofthe optical shutter system, where the movement is horizontal, are afunction of the height of the transparency 2 and the expected viewingdistance EVD. Thus a light source placed at a distance from thetransparency equal to the expected viewing distance should extend twiceas far from the viewing axis in both directions as the transparency. Ina typical optical shutter system having two reflective surfaces, thefirst reflector 60 is one-seventh of the way to the light source andthus has a height I percent of the height of the transparency from theviewing axis; the second reflector 62 is two-thirds of the way to thelight source and thus has a height equal to 167 percent of the height ofthe transparency from the viewing axis. This, of course, makes noallowance for variations in the vertical location of the viewer asindicated by arrows 61 and 63. Additional height of all elements must beprovided to accommodate a range of viewing heights.

In all embodiments, front silvered mirrors are preferably used as thereflective surfaces to prevent diffusion of the reflected linear lightand a ghost from the front surface. Moreover, the lamp used as the lightsource is preferably operated on direct current (DC) or a very highfrequency as the shutter system displays a wave impression duringoperation on AC and at 60 Hertz this wave can be noticeable. At highrelative speeds, it could even be irritating and damage the visualeffects.

A concave reflector 70 shown in FIG. 8 may replace the planar reflectivesurfaces, especially where both depth and lateral spacing are limited. Acurved reflector places the virtual image of the light source in anydesired position, while greatly shortening the rays from the lightsource. As is well understood, a convex reflector would provide anopposite result. While the curvature and angular disposition of thereflector can be derived mathematically, the curvature of the reflectoris readily derived utilizing an empirical method illustrated in FIG. 9.The transparency and light source are positioned, the estimated viewingdistance is established, and the virtual image position is locatedbehind the transparency, preferably at a distance substantially equal tothe estimated viewing distance. Rays ML through QL are drawn from thetransparency 2 to the virtual light L. To determine the points on therays ML through QL where the curved reflecting surface lies, a firstline RS is drawn parallel to the transparency from the linear lightsource 6 to the farthest ray QL. The angle RSL interior to both thevirtual and real positions of the light source is bisected and thebisector ST is extended to intersect the next ray PL at point T. Thesetwo points of intersection S and T both lie on the curved reflectingsurface 70. A line RT is drawn from the light source 6 to thisnow-defined point of intersection T, and the angle RTL between line RTand the ray PL is bisected. This bisector TU is extended to the next ray0L and intersection U also lies on the curved reflecting surface '70.This process continues until points are defined on each ray ML throughQL, defining the curvature of reflecting surface 70. The accuracy ofdefinition of the curvature is a function of the number of rays selectedand constructed from the transparency 2 to the virtual light L. A singlesmooth curve is then drawn connecting these points and this provideswhat is in effect a combination of a convex lens and a canted mirror toboth shorten the position of the virtual light source L and relocate itin the folded position R. A baffle 65 is preferably disposed at point Mto avoid direct impingement of light from source 6 on sheet 2.

A single light source may supply the linear light for adjacent opticalassemblies using curved reflectors as shown in FIGv 10. The curvature ofthe left surface half 68 is derived in the same fashion as the righthalf 70. An observer moving from right to left past the assembly 72including the associated transparencies 2e and 2f perceives successivesegments of the first image 2f from right to left and then the secondimage 2e. Thus the system using curved mirrors functions in essentiallythe same fashion as the system of FIG. I. Baffles (not shown) are alsodisposed between the light and the edge of the transparency.

One particular application of the optical shutter system is illustrateddiagrammatically in FIGS. Ill and I2. Therein a virtual light source 6Vis shown located behind the vertical wall 71 of a subway cavity whichhas mounted thereon as assembly 72 for use with the optical shuttersystem described herein. A subway train 74 moves on tracks 76 which aresupported on subway floor 78 and thus a rigid viewing platform isestablished relative to the assembly 72. The viewer may be at variouspoints in the subway train 74 and observe the display assembly 72through the train window 80. For example, the viewing position of aseated passenger is indicated diagrammatically by eye 82 and that of astanding passenger by eye 84.

As is apparent from the broken line viewing angle 86 for the seatedpassenger and the broken line viewing angle 88 for the standingpassenger, optimum viewing will be available to all of them providedonly that all of the reflective surfaces and the light sourcerepresented by virtual source 6V are properly proportioned to fill theentire height between the extremes of the viewing angles. The selectionof a viewing distance for the position of the virtual light source 6V ispreferably about equal to the maximum distance of a viewer, such asstanding viewer 84, from the image on pellucid sheet 90. With thiscriteria the proportions should be satisfactory for all viewingdistances less than this maximum, and will improve the reproduction forthe sitting viewer 82.

FIG. 12 shows the same diagrammatic subway system but illustrates howthe sitting viewer 82 will see a continuous reconstruction of the imageas he moves from the solid line position 82a to the broken line position8212. In the case ofa passenger who is more distant from the pellucidsheet 90, such as standing passenger 84, he will actually see an initialline segment of the image of sheet 90a when he is at position 84a andwill at the same time be seeing a central line segment preceding image90b as he moves in the direction of arrow 92, When this viewer reachespoint 8417 (when the train has reaches the broken line position 74b),viewer 84 will see the final left hand line segment of image 90b (whichis the right hand line seg ment of the actual visual impression on theviewer). Shortly thereafter he will begin to see the first line segmentof image 90. As already explained, because of the speed of relativetravel and the image retention of the human retina and sensory system,the viewer is unaware of the segmenting of the images and sees only asingle full field image. If the images vary in an animated sequence, theviewer will receive a mental impression of animation very much like thatof a motion picture.

The system is operative for a wide range of relative speeds of the sheetand viewer provided only that the speed is sufficient to provide acontinuous visual impression based upon the persistence of the eye.Furthermore, the system may be experiencing either acceleration ordeceleration over a wide range without adverse affects. The onlysignificant effect on the visual impression is in the case of animateddisplays where the animation is either retarded or accelerated. Eitherthe viewer or sheet and light assembly may be moving in an arcuate path,or the two may be converging or separating and the visual impressionwill be substantially the same. However, if such variations aresubstantial it may be desirable to take them into account in the designof the shutter system assembly.

For maximum optical resolution the light source should be as narrow aspossible, preferably having no perceptible width. However, in generalthe amount of light available is directly related to the width of thesource and thus these two parameters are balanced in a given design toprovide maximum image resolution with optimum light intensity. The lightmay be baffled or otherwise treated to provide an adjustable width, ifso desired.

While several particular embodiments of this invention are shown aboveand described, it will be understood, of course, that the invention isnot to be limited thereto, since many modifications may be made.Specifically, excellent results have been obtained by mounting thepellucid sheets, optics and light source for movement relative to afixed view. It is contemplated, therefore, by the appended claims, tocover any such modifications as fall within the true spirit and scope ofthis invention.

lclaim:

1. In an arrangement for providing a viewer with a sequentiallyconstructed visual effect of an image, the combination comprising apellucid sheet on which said image is reproduced, a source of lightmounted in spaced relationship on one side of said sheet and providing anarrow elongate radiating light source generally parallel to said sheet,means supporting said viewer and said sheet in spaced relationship withsaid viewer disposed on the side of said sheet opposite said lightsource, and means providing relative movement between said viewer andsaid sheet, said movement being generally parallel to said sheet andnormal to said light source whereby said viewer sees said narrowelongate light source through only a given segment of said image bearingsheet at any given instant of time and the relative movement of saidviewer and said sheet sequentially exposes said elongate light source toview through adjacent segments of said image bearing sheet whereby theimage is constructed as a complete visual effect for the viewer as saidviewer and sheet move relatively.

2. The arrangement of claim 1 wherein said image bearing pellucid sheetis a photographic transparency.

3. The arrangement of claim 1 wherein said sheet is a substantiallyplanar rectangle.

4. The arrangement of claim 3 wherein said sheet is mounted in asubstantially vertical position, said light source is mountedsubstantially vertically and parallel to said sheet and the relativemovement of said viewer and said sheet is substantially horizontal andparallel to said sheet.

5. The arrangement of claim 1 wherein the effective spacing between saidsheet and said light source is substantially equal to the normaldistance between said sheet and said viewer.

6. The arrangement of claim 1 wherein said sheet and light source arefixed and the means for providing relative movement between the sheetand the viewer is a movable vehicle.

7. The arrangement of claim 5 wherein said sheet and said light sourceare fixed and the means for providing relative movement is a wheeledpassenger carrying vehicle.

8. The arrangement of claim 7 for use in a'subway system having wallsand wheeled vehicles, said sheet and light source being mounted on awall of said subway and said wheeled vehicles moving generally parallelto said wall.

9. The arrangement of claim 1 including a plurality of sheets in alignedrelationship and an elongate narrow light source cooperating with eachof said sheets, said sheets being aligned on an axis generally parallelto the direction of relative movement.

10. The arrangement of claim 8 including a plurality of sheets inaligned relationship along said wall, said wheeled vehicles havingwindows and said windows and sheets being aligned whereby said lightsources can be viewed through said sheets and said windows.

11. The arrangement of claim 9 wherein all of said plurality of sheetshave the same image thereon whereby the viewer is provided with a singlesustained visual effect.

12. The arrangement of claim 9 wherein each of said sheets has an imagethereon related to but different from the images on the adjacent sheetswhereby an animated visual effect is provided the viewer.

13. The arrangement of claim 1 wherein the light source is longer thanthe corresponding generally parallel dimension of the sheet whereby theviewer will see the light source through substantially the entire areaof said sheet.

14. The arrangement of claim 1 wherein a reflective surface is disposedin a generally overlying relationship to said sheet on the side of saidsheet opposite said viewer, and said light source is aligned with saidreflective surface whereby the light source is viewed on the reflectivesurface through said sheet as the viewer and sheet move relativelywhereby a virtual light source is provided on the side of said sheetopposite the viewer.

15. The arrangement of claim 14 wherein said light source is disposedadjacent and generally parallel to one edge of said sheet, baffle meansare provided to prevent the impingement of light directly from saidsource onto said sheet and said reflective surface is oriented toprovide visual observation of said light source through said sheet andfrom said reflective surface as said sheet and said viewer moverelatively.

16. The arrangement of claim 15 wherein a plurality of reflectivesurfaces are employed with said sheet and said light source to provide areflective system adjacent said sheet to reduce the depth of saidarrangement.

17. The arrangement of claim 16 wherein two adjacent sheets are providedwith a single light source therebetween, each of said sheets beingprovided with a baffle and a reflective system associated with saidlight source.

18. The arrangement of claim 15 wherein said reflective means is acylindrical reflector curved about an axis parallel to said light sourceto provide a substantially complete sequential construction of saidimage with reduced depth of said arrangement.

19. A method for projecting a sequentially constructed visual effect ofan image reproduced on a pellucid sheet and illuminated by a source ofnarrow elongate light to a viewer where there is relative motion betweenthe viewer and the sheet generally parallel to the sheet and normal tosaid light source so that the elongate light appears to sweep laterallyacross said pellucid sheet presenting successive segments of the imageon the sheet to the viewer, said method comprising establishing thelateral boundaries of the pellucid sheet, positioning the elongatesource of light in spaced relationship on one side of the sheet,establishing the position of the virtual position of the light sourcebehind the sheet so that the boundaries of the sheet and the lightsource define a triangle, folding the triangle so that its apex rests onthe actual position of the source of light, and placing a planarreflective surface in the vertical plane defined by the crease in thetriangle so that the light source appears to the observer at theselected virtual image position and is viewed sequentially throughadjacent segments of said sheet to construct said image,

20. A method for projecting a sequentially constructed visual effect ofan image, reproduced on a pellucid sheet and illuminated by a source ofa narrow elongate light radiating generally parallel to said sheet, to aviewer in motion generally parallel to the sheet and normal to saidlight source, said method comprising establishing the real position ofthe elongate light source and its virtual position relative to thepellucid sheet, defining paths for light rays from the virtual positionto the sheet, drawing a first line from the light source real positionto the farthest ray at a predetermined point spaced from said sheet,bisecting the angle defined by said first line and said ray and interiorto the real and virtual positions of the light source, extending thebisector to an intersection with the adjacent ray, drawing a second linefrom the light source position to the intersection, bisecting theinterior angle defined and extending the bisector to an intersectionwith the adjacent ray, repeating the process for all the rays, andplacing a smoothly curved cylindrical reflective surface in the verticalplane defined by these points of intersection so that elongate lightappears to sweep laterally across said sheet as the viewer and sheetmove relatively presenting successive segments of the sheet to theviewer whereby the image is reconstructed as a complete visual effect.

21. In an arrangement for providing a sequentially constructed visualeffect of an image to a viewer in relative motion parallel to thearrangement, the combination comprising a housing, a pellucid sheet onwhich said image is reproduced mounted in an opening in said housing, asource of light mounted in spaced relationship adjacent one edge of saidsheet within said housing and providing radiating light source generallyparallel to said sheet, and a reflective surface disposed in a generallyaligned relationship to said sheet within said housing, said lightsource being aligned with said reflective surface and said reflectivesurface being oriented so that the light source is viewed on thereflective surface through said sheet for each position of said vieweroutside of said housing and spaced from said sheet whereby said elongatelight source is exposed to view through segments of said image bearingpellucid sheet determined by the positions of the viewer, and the imageis constructed as a complete visual effect for the viewer whenever theviewer and sheet move relatively so that the viewer assumes allpositions across the opening in said housing.

22. The arrangement of claim 21 wherein said light source is disposedadjacent and generally parallel to one edge of said sheet, baffle meansare provided within said housing to a narrow elongate prevent theimpingement of light directly from said source onto said sheet and saidreflective surface is oriented to provide visual observation of saidlight source through said sheet and from said reflective surface as saidsheet and said viewer move relatively.

23. The arrangement of claim 22 wherein a plurality of reflectivesurfaces are disposed within said housing and employed with said sheetand said light source to provide a multiple stage reflective systemadjacent said sheet to reduce the depth and width of said arrangement.

24. The arrangement of claim 23 wherein two adjacent sheets are providedin said housing with a single light source therebetween, each of saidsheets being provided with a baffle and a reflective system associatedwith said light source.

25. The arrangement of claim 22 wherein said reflective means is acylindrical reflector curved about an axis parallel to said light sourceto provide a substantially complete and undistorted sequentialconstruction of said image with reduced depth of said arrangement.

1. In an arrangement for providing a viewer with a sequentiallyconstructed visual effect of aN image, the combination comprising apellucid sheet on which said image is reproduced, a source of lightmounted in spaced relationship on one side of said sheet and providing anarrow elongate radiating light source generally parallel to said sheet,means supporting said viewer and said sheet in spaced relationship withsaid viewer disposed on the side of said sheet opposite said lightsource, and means providing relative movement between said viewer andsaid sheet, said movement being generally parallel to said sheet andnormal to said light source whereby said viewer sees said narrowelongate light source through only a given segment of said image bearingsheet at any given instant of time and the relative movement of saidviewer and said sheet sequentially exposes said elongate light source toview through adjacent segments of said image bearing sheet whereby theimage is constructed as a complete visual effect for the viewer as saidviewer and sheet move relatively.
 2. The arrangement of claim 1 whereinsaid image bearing pellucid sheet is a photographic transparency.
 3. Thearrangement of claim 1 wherein said sheet is a substantially planarrectangle.
 4. The arrangement of claim 3 wherein said sheet is mountedin a substantially vertical position, said light source is mountedsubstantially vertically and parallel to said sheet and the relativemovement of said viewer and said sheet is substantially horizontal andparallel to said sheet.
 5. The arrangement of claim 1 wherein theeffective spacing between said sheet and said light source issubstantially equal to the normal distance between said sheet and saidviewer.
 6. The arrangement of claim 1 wherein said sheet and lightsource are fixed and the means for providing relative movement betweenthe sheet and the viewer is a movable vehicle.
 7. The arrangement ofclaim 5 wherein said sheet and said light source are fixed and the meansfor providing relative movement is a wheeled passenger carrying vehicle.8. The arrangement of claim 7 for use in a subway system having wallsand wheeled vehicles, said sheet and light source being mounted on awall of said subway and said wheeled vehicles moving generally parallelto said wall.
 9. The arrangement of claim 1 including a plurality ofsheets in aligned relationship and an elongate narrow light sourcecooperating with each of said sheets, said sheets being aligned on anaxis generally parallel to the direction of relative movement.
 10. Thearrangement of claim 8 including a plurality of sheets in alignedrelationship along said wall, said wheeled vehicles having windows andsaid windows and sheets being aligned whereby said light sources can beviewed through said sheets and said windows.
 11. The arrangement ofclaim 9 wherein all of said plurality of sheets have the same imagethereon whereby the viewer is provided with a single sustained visualeffect.
 12. The arrangement of claim 9 wherein each of said sheets hasan image thereon related to but different from the images on theadjacent sheets whereby an animated visual effect is provided theviewer.
 13. The arrangement of claim 1 wherein the light source islonger than the corresponding generally parallel dimension of the sheetwhereby the viewer will see the light source through substantially theentire area of said sheet.
 14. The arrangement of claim 1 wherein areflective surface is disposed in a generally overlying relationship tosaid sheet on the side of said sheet opposite said viewer, and saidlight source is aligned with said reflective surface whereby the lightsource is viewed on the reflective surface through said sheet as theviewer and sheet move relatively whereby a virtual light source isprovided on the side of said sheet opposite the viewer.
 15. Thearrangement of claim 14 wherein said light source is disposed adjacentand generally parallel to one edge of said sheet, baffle means areprovided to prevent the impingement of light directly from said sourceonto said sheet and said reflective surface is oriented to providevisual observation of said light source through said sheet and from saidreflective surface as said sheet and said viewer move relatively. 16.The arrangement of claim 15 wherein a plurality of reflective surfacesare employed with said sheet and said light source to provide areflective system adjacent said sheet to reduce the depth of saidarrangement.
 17. The arrangement of claim 16 wherein two adjacent sheetsare provided with a single light source therebetween, each of saidsheets being provided with a baffle and a reflective system associatedwith said light source.
 18. The arrangement of claim 15 wherein saidreflective means is a cylindrical reflector curved about an axisparallel to said light source to provide a substantially completesequential construction of said image with reduced depth of saidarrangement.
 19. A method for projecting a sequentially constructedvisual effect of an image reproduced on a pellucid sheet and illuminatedby a source of narrow elongate light to a viewer where there is relativemotion between the viewer and the sheet generally parallel to the sheetand normal to said light source so that the elongate light appears tosweep laterally across said pellucid sheet presenting successivesegments of the image on the sheet to the viewer, said method comprisingestablishing the lateral boundaries of the pellucid sheet, positioningthe elongate source of light in spaced relationship on one side of thesheet, establishing the position of the virtual position of the lightsource behind the sheet so that the boundaries of the sheet and thelight source define a triangle, folding the triangle so that its apexrests on the actual position of the source of light, and placing aplanar reflective surface in the vertical plane defined by the crease inthe triangle so that the light source appears to the observer at theselected virtual image position and is viewed sequentially throughadjacent segments of said sheet to construct said image.
 20. A methodfor projecting a sequentially constructed visual effect of an image,reproduced on a pellucid sheet and illuminated by a source of a narrowelongate light radiating generally parallel to said sheet, to a viewerin motion generally parallel to the sheet and normal to said lightsource, said method comprising establishing the real position of theelongate light source and its virtual position relative to the pellucidsheet, defining paths for light rays from the virtual position to thesheet, drawing a first line from the light source real position to thefarthest ray at a predetermined point spaced from said sheet, bisectingthe angle defined by said first line and said ray and interior to thereal and virtual positions of the light source, extending the bisectorto an intersection with the adjacent ray, drawing a second line from thelight source position to the intersection, bisecting the interior angledefined and extending the bisector to an intersection with the adjacentray, repeating the process for all the rays, and placing a smoothlycurved cylindrical reflective surface in the vertical plane defined bythese points of intersection so that elongate light appears to sweeplaterally across said sheet as the viewer and sheet move relativelypresenting successive segments of the sheet to the viewer whereby theimage is reconstructed as a complete visual effect.
 21. In anarrangement for providing a sequentially constructed visual effect of animage to a viewer in relative motion parallel to the arrangement, thecombination comprising a housing, a pellucid sheet on which said imageis reproduced mounted in an opening in said housing, a source of lightmounted in spaced relationship adjacent one edge of said sheet withinsaid housing and providing a narrow elongate radiating light sourcegenerally parallel to said sheet, and a reflective surface disposed in agenerally aligned relationship to said sheet within said housing, saidlighT source being aligned with said reflective surface and saidreflective surface being oriented so that the light source is viewed onthe reflective surface through said sheet for each position of saidviewer outside of said housing and spaced from said sheet whereby saidelongate light source is exposed to view through segments of said imagebearing pellucid sheet determined by the positions of the viewer, andthe image is constructed as a complete visual effect for the viewerwhenever the viewer and sheet move relatively so that the viewer assumesall positions across the opening in said housing.
 22. The arrangement ofclaim 21 wherein said light source is disposed adjacent and generallyparallel to one edge of said sheet, baffle means are provided withinsaid housing to prevent the impingement of light directly from saidsource onto said sheet and said reflective surface is oriented toprovide visual observation of said light source through said sheet andfrom said reflective surface as said sheet and said viewer moverelatively.
 23. The arrangement of claim 22 wherein a plurality ofreflective surfaces are disposed within said housing and employed withsaid sheet and said light source to provide a multiple stage reflectivesystem adjacent said sheet to reduce the depth and width of saidarrangement.
 24. The arrangement of claim 23 wherein two adjacent sheetsare provided in said housing with a single light source therebetween,each of said sheets being provided with a baffle and a reflective systemassociated with said light source.
 25. The arrangement of claim 22wherein said reflective means is a cylindrical reflector curved about anaxis parallel to said light source to provide a substantially completeand undistorted sequential construction of said image with reduced depthof said arrangement.